1. Field of the Invention
The present invention relates to a capsule type medical device including a swallowable capsule and an external unit of receiving living body information sent from the capsule.
2. Description of the Related Art
Recently, a capsule type device has been proposed whereby a capsule body in capsule form is inserted into a body cavity for examination.
For example, according to a first technology of the related art, disclosed in Japanese Unexamined Patent Application Publication No. 7-111985, a spherical capsule, which is divided into two, is used to communicate living body information to an external device via a communication unit.
However, the example of the related art does not consider the proper transmission of living body information from the capsule side to the external device side.
Thus, the capsule side has to send living body information with higher transmission power as much as possible so that the external device side can receive the information surely. In this case, electric energy in a battery built in the capsule is consumed largely, thus shortening the capsule usable time.
It may be considered that the transmission power is reduced in order to increase the lifetime of the battery. In this case, however, the information cannot be received by the external device side fully.
A second technology of the related art disclosed in the Japanese Unexamined Patent Application Publication No. 2001-46357 is a system for receiving signals from the capsule side at a plurality of antennas in the external unit side in order to obtain living body information including position information.
Furthermore, a third technology of the related art disclosed in the U.S. Pat. No. 5,604,531 is a system for receiving signals corresponding to an image sent from the capsule to the external device side by a plurality of antennas in order to select an antenna, which has the largest signal strength.
In this case, a plurality of antenna are used and an antenna, which has the largest signal strength, is selected so that the signals from the capsule can be received more surely than the case using one antenna. However, like the case of the first technology of the related art, it is not arranged so as to set the proper transmission power on the capsule side.